The invention is in the field of automatic control systems of the type increasingly used in industry, and in particular pertains to a means of automatically replenishing water in a number of vats which lose water due to evaporation or any other cause. The particular system disclosed and claimed herein relates to an eyeglass lens tinting system in which a number of vats, nine in the illustrated embodiment and common in the industry, each contains a water-based dye of a different color, with one of the vats possibly containing a bleach or color neutralizing solution.
During the tinting of the eyeglass lenses, generally done by an optical company, an optician or even an optometrist with a small tinting setup in a back office, the eyeglass lenses are typically either immersed in the dye for a continuous tint throughout the surface of the lens, or reciprocated up and down to various levels to create a gradient tint.
The dye solution in these vats is maintained at a temperature just under the boiling point between 200.degree. and 210.degree. Fahrenheit. This high temperature causes a considerable evaporation rate. Because each vat requires separate replenishment according to its own needs, replenishing the water is considered a time-wasting nuisance by the technician, who generally waits until the water level has fallen 1/2" to 1", before replenishing the vats.
Because the dye solution level is so low when it is replenished, and the replenishing water is generally at about room temperature since it is usually bottled distilled or purified water, the replenishing causes a considerable temperature drop in the vat. Once the temperature has been dropped in this fashion, the technician must wait until it returns to the 200.degree. to 210.degree. Fahrenheit level before he can continue using the vat or vats in question.
Additionally, because vat dye level maintenance is currently done manually and is not automated, the dye unit in general must never be left unattended for any period of time. There is a possibility that the unit might boil over, spilling water into the expensive heat conducting fluid that circulates beneath the vats in the vat housing manifold. Additionally, should the unit be left unattended for several hours, it is possible that one or more of the vats could dry up, producing toxic vapors.
Because almost all dye units use quart-size vats, there is not adequate room for a float-type level control system of the kind used in water closets.
There is a need, therefore, for a better system to monitor the dye fluid level in each vat, refilling the vat when necessary, and alerting the operator in the event of a boil-over or flood condition, and preferably shutting both the dye unit and the replenishing system off in such an event.